1. Field of the Invention
The present invention relates to a wheel alignment measuring device and wheel alignment measuring method for measuring wheel alignment to three-dimensionally detect displacement and inclination of a wheel of a driven vehicle with a vehicle basic characteristics detecting device.
2. Related Art
A vehicle basic characteristics detecting device is known as a test device for measuring the basic characteristics of a vehicle, such as suspension characteristics or steering characteristics, in a test chamber.
In such a vehicle basic characteristics detecting device, the vehicle to be measured is fixed in a predetermined position, and rotational force, horizontal force, and vertical force are applied to the wheels. By processing the measurement data obtained from the reaction force, the basic characteristics can be detected.
As a part of the vehicle basic characteristics detecting device, there is a wheel alignment measuring device for measuring wheel alignment, such as spin angle, camber angle, and toe angle, based on the distance from a reference position to the side surface of the wheel.
A conventional wheel alignment measuring device is fixed onto a platform which supports the wheel and is driven by an actuator. Being connected to the wheel, it generally detects movement of the wheel. The problem with this type of mechanical wheel alignment measuring device is that measurements cannot be made at high speed because of a decrease in measuring accuracy caused by friction of the moving parts and restrictions due to the inertial mass of the components or the like.
To solve the problem, a non-contact type wheel alignment measuring device provided with a non-contact type distance sensors such as laser beam sensors and ultrasonic sensors.
More specifically, a conventional optical wheel alignment measuring device comprises a measuring unit provided with a plurality of optical sensors (laser displacement gauges, for instance). This measuring unit is disposed on the platform on the side of a wheel. The distance from a predetermined reference position to the measuring plate attached to the side surface of the wheel is optically measured by moving the measuring unit in the longitudinal direction of the vehicle. Based on the obtained measurement data, the camber angle and toe angle are determined.
In the optical wheel alignment measuring device of the first example, the measuring plate is attached to the wheel with a jig which is provided to the wheel beforehand. An adjuster of the attachment jig adjusts the center of the attachment jig to the center of the wheel. A fitting provided to the measuring plate for restricting the attachment position is then connected to the attachment jig by a magnet provided to the attachment jig.
With the wheel alignment measuring device of the first example, the position of the measuring plate needs to be adjusted by the adjuster of the attachment jig, which is time-consuming.
Due to the attachment jig, the distance from the center of the width of the wheel to the measuring surface of the target plate becomes longer, i.e., the radius of the rotational axis of the measuring surface becomes larger. So, if the wheel inclines at a large angle, or if the camber angle greatly varies during the measurement, the amount of movement of the measuring surface becomes large. This results in a problem that the area of the limited measuring surface cannot be effectively utilized.
Also, the laser displacement gauges of the first example of the prior art are driven in a two-dimensional stage based on the origin of the measuring plate, so that the laser displacement gauges follow the movement of the measuring plate, and that the laser beam is always emitted onto the measuring plate.
As a result, the structure of the device becomes complicated, and the manufacturing cost becomes high.
Also, the two-dimensional driving control operation for driving the laser displacement gauges becomes complicated, so does the adjustment operation of the laser displacement gauges for improving the measuring accuracy.
In an optical wheel alignment measuring device of the second example of the prior art, three laser displacement gauges are employed for measuring the camber angle and toe angle. Two of the laser displacement gauges are a first laser displacement gauge and a second laser displacement gauge. The first laser displacement gauge irradiates measuring light onto a position at a first predetermined distance from the rotational center of the wheel in a first horizontal direction on the measuring plate. The second laser displacement gauge irradiates the measuring light onto a position at a second predetermined distance in the vertical direction. The remaining third laser displacement gauge irradiates the measuring light onto a position at a third predetermined distance from the rotational center in a second horizontal direction opposite from the first horizontal direction. The position irradiated by the third laser displacement gauge is situated on a line perpendicular to the vertical line extending through the rotational center.
In such a case, the camber angle is calculated from the displacement difference between the distance from the measuring plate measured by the first laser displacement gauge and the distance from the measuring plate measured by the second laser displacement gauge, and the distance LZxe2x80x2 between the laser beam irradiation point of the first laser displacement gauge and the laser beam irradiation point of the second laser displacement gauge.
More specifically, the camber angle xcex8CAM can be calculated by the following formula:
xcex8CAM=tanxe2x88x921(|L1xe2x88x92L2|)/LZxe2x80x2
where the distance from the measuring plate measured by the first laser displacement gauge is L1, and the distance from the measuring plate measured by the second laser displacement gauge is L2.
The toe angle is calculated from the displacement difference between the distance from the measuring plate measured by the third laser displacement gauge and the distance from the measuring plate measured by the first (or second) laser displacement gauge, and the distance LX between the laser beam irradiation point of the third laser displacement gauge and a line in parallel with the Z-direction (vertical direction) including the laser beam irradiation point on a plane containing the laser beam irradiation point of the first (or second) laser displacement gauge.
More specifically, the camber angle xcex8CAM can be calculated by the following formula:
xcex8CAM=tanxe2x88x921(|L3xe2x88x92L1|)/LX
where the distance from the measuring plate measured by the third laser displacement gauge is L3, and the distance from the measuring plate measured by the first laser displacement gauge is L1.
In this case, even if the amount of movement in the Z direction is large, the distance LZxe2x80x2 between the first laser displacement gauge and the second laser displacement gauge cannot be made long.
This is because the laser beam emitted from all the laser displacement gauges is required to irradiate the measuring plate in the camber angle and toe angle measurement, in both cases where the measuring plate is situated in the highest possible position in the Z direction and where the measuring plate is situated in the lowest possible position in the Z direction.
In other words, the laser beam irradiation points of all the laser displacement gauges should exist within an area surrounded by the highest possible position and the lowest possible position that the measuring light from the laser displacement gauges can be emitted onto the measuring plate.
As a result, the measuring accuracy of the camber angle xcex8CAM cannot be ensured.
On the other hand, if the measuring accuracy of the camber angle xcex8CAM is increased, the distance LZxe2x80x2 between the laser beam irradiation point of the first laser displacement gauge and the laser beam irradiation point of the second displacement gauge needs to be long. As a result, the measurable range, which is the difference between the highest possible position and the lowest possible position, cannot be made wide.
A ultrasonic wheel alignment measuring device of the third embodiment of the prior art is provided with a plurality of ultrasonic sensors in predetermined positions on the side of the wheel. The ultrasonic sensors measure the distance from a predetermined reference position to the measuring plate attached to the side surface of the wheel. Based on the obtained measurement data, the camber angle and toe angle are determined. Japanese Utility Model Laid-Open No. 63-44107 discloses more details.
An optical wheel alignment measuring device of the fourth embodiment of the prior art is provided, on a platform on the side of a wheel, with a measuring unit comprising a plurality of optical sensors (laser displacement gauges, for instance). The measuring unit moves in the longitudinal direction of the vehicle so as to optically measure the distance from a predetermined reference position to the measuring plate attached to the side surface of the wheel. Based on the obtained measurement data, the camber angle and toe angle are determined. Japanese Patent Laid-Open No. 63-94103 discloses more details.
The ultrasonic wheel alignment measuring device of the third embodiment of the prior art is capable of measuring a large amount of displacement, but the allowable range of the inclination of the sensor axis of each ultrasonic sensor is xc2x17xc2x0 from the limit of the reflection angle. Also, the ultrasonic wheel alignment measuring device cannot be used in wheel alignment measurement whose inclination range is wide.
In the case of the optical wheel alignment measuring device with the laser displacement gauges of the fourth embodiment of the prior art, it is difficult to have a measurable displacement range (measurable distance range) of xc2x1100 mm, with a reference distance set between the measuring surface of the measuring plate and the laser displacement gauges. Setting such a measuring displacement range will result in low accuracy and high cost. For this reason, an optical wheel alignment measuring device in practical use is fixed onto a platform, so that laser displacement gauges of small measurable displacement range can be used in measurement.
In such a case, the wheel alignment to be actually measured is the alignment with respect to the vehicle body.
With the vehicle body being fixed onto a predetermined reference position, even if the platform is displaced with respect to the reference position by starting the actuator, the relative positional relationship between the platform and the wheel alignment measuring device will not change, and the wheel alignment measurement data should include the amount of displacement of the platform.
However, the amount of displacement of the platform contains errors caused by rigid deformation of the platform, and such errors cannot be excluded from the measurement data. This results in inaccurate wheel alignment measurement, with the measurement data containing measurement errors.
To exclude the measurement errors, data correction can be performed. However, error causing conditions greatly vary, and appropriate correction cannot always be performed, which results in poor measuring accuracy, reliability, and reproducibility.
Since the amount of platform displacement cannot be excluded from the measurement data, the measurement data end up including measurement errors, which hinders accurate wheel alignment measurement.
To exclude the measurement errors, data correction can be performed. However, measuring conditions greatly vary, and appropriate correction cannot always be performed, which results in poor measuring accuracy, reliability, and reproducibility.
To solve the above problems, a first object of the present invention is to provide a wheel alignment measuring device and a wheel alignment measuring method which can make a wheel alignment measurement with a simpler structure at a lower manufacturing cost. By this device and method, the adjustment of the measuring plate becomes simpler, and the rotational radius of the measuring surface is minimized so that the area of the measuring surface can be effectively utilized.
A second object of the present invention is to provide a wheel alignment measuring device and a wheel alignment measuring method with a simpler structure at a lower manufacturing cost. By this device and method, control and adjustment operations become easier.
A third object of the present invention is to provide a wheel alignment measuring device and a wheel alignment measuring method with a simpler structure and a simpler control procedure. By this device and method, wheel alignment measurements can be taken at high speed, and the measuring accuracy of the camber angle xcex8CAM is maintained.
A fourth object of the present invention is to provide a caster angle measuring device, a wheel alignment measuring device, a caster angle measuring method, and a wheel alignment measuring method. By these devices and methods, a non-contact caster angle can be measured with a desired accuracy.
A fifth object of the present invention is to provide a measuring plate, a wheel alignment measuring device, and a wheel alignment measuring method, by which the positional relationship between the measuring plate and the wheel alignment measuring device can be constantly and quickly detected. Thus, accuracy, reliability, and reproducibility in wheel alignment measurement can be improved.
A sixth object of the present invention is to provide a measuring plate, a wheel alignment measuring device, and a wheel alignment measuring method, by which the positional relationship between the measuring plate and the wheel alignment measuring device can be surely and quickly detected. Thus, accuracy, reliability, and reproducibility in alignment measurement can be improved.
To achieve the first object, the present invention provides a wheel alignment measuring device which measures wheel alignment using a measuring plate provided with a rotational center specifying mark on the measuring surface thereof and attached to a wheel of a vehicle being measured. This wheel alignment measuring device comprises: a caster angle detecting unit for detecting a caster angle of the measuring plate; a mark coordinate detecting unit for detecting mark coordinates which are the coordinates in an absolute space of the rotational center specifying mark; and a rotational center coordinate calculating unit for calculating current rotational center coordinates which are the coordinates of a current rotational center of the measuring surface of the measuring plate in the absolute space.
According to this embodiment, the rotational center coordinate calculating unit calculates the current rotational center coordinates in the absolute space of the measuring surface of the measuring plate based on the caster angle detected by the caster angle detecting unit and the mark coordinates detected by the mark coordinate detecting unit. Thus, accurate wheel alignment measurements can be taken by detecting the rotational center position of the wheel, without attaching the measuring plate in line with the rotational center in advance.
Also, there is no need to provide the measuring plate with a jig for adjusting the rotational center position. This reduces the thickness of the measuring plate in the transverse direction of the vehicle being measured. Thus, the rotational radius of the wheel at the time of a toe angle change can be made smaller, so that the area of the measuring surface of the measuring plate can be effectively utilized.
In a preferred embodiment of the present invention the rotational center coordinate calculating unit comprises: a real mark coordinate calculating unit for calculating reference mark coordinates which are current initial mark coordinates corresponding to the coordinates of the rotational center specifying mark with the origin being initial rotational coordinates corresponding to the initial values of the rotational center coordinates, based on the caster angle and the mark coordinates; and a current center coordinate calculating unit for calculating the current rotational center coordinates based on the reference mark coordinates.
According to this embodiment, the real mark coordinate calculating unit of the rotational center coordinate calculating unit calculates the reference mark coordinates, which are the current coordinates of the initial mark coordinates that are the coordinates of the rotational center specifying mark predetermined as the origin, and the current center coordinate calculating unit calculate the current rotational center coordinates based on the reference mark coordinates determined by the real mark coordinate calculating unit. Thus, the rotational center position of the wheel can be calculated from only a small amount of data.
In a preferred embodiment of the present invention the real mark coordinate calculating unit calculates the reference mark coordinates using formulas (1) and (2):
X0xe2x80x3=X0xe2x80x2 cos(xcex8CAS)+Z0xe2x80x2 sin(xcex8CAS)xe2x80x83xe2x80x83(1)
Z0xe2x80x3=xe2x88x92X0xe2x80x2 sin(xcex8CAS)+Z0xe2x80x2 cos(xcex8CAS)xe2x80x83xe2x80x83(2)
and the current center coordinate calculating unit calculates the current rotational center coordinates (X0, Z0) using formulas (3) and (4):
X0=X0xe2x80x2xe2x88x92X00+XXxe2x80x83xe2x80x83(3)
Z0=Z0xe2x80x3xe2x88x92Z00+ZZxe2x80x83xe2x80x83(4)
where the caster angle measured counterclockwise is xcex8CAS, the mark coordinates are (X0xe2x80x2, Z0xe2x80x2), the reference mark coordinates are (X0xe2x80x3, Z0xe2x80x3), the initial mark coordinates are (X00, Z00), and the initial rotational center coordinates are (XX, ZZ).
According to this embodiment, the real mark coordinate calculating unit calculates the reference mark coordinates using the formulas (1) and (2), and the current center coordinate calculating unit calculates the current rotational center coordinates (X0, Z0) using the formulas (3) and (4). Thus, the rotational center position can be given by simple formulas, and real time processing can be performed without complicating the control operation of the arithmetic operation unit.
In a preferred embodiment of the present invention measuring wheel alignment is performed using a measuring plate provided with a rotational center specifying mark on its measuring surface and attached to a wheel of a vehicle being measured. This method comprises: a caster angle detecting step of detecting the caster angle of the measuring plate; a mark coordinate detecting step of detecting mark coordinates which are the coordinates of the rotational center specifying mark in an absolute space; and a rotational center coordinate calculating step of calculating current rotational center coordinates which are the rotational center coordinates of the measuring surface of the measuring plate in the absolute space at present, based on the detected caster angle and the mark coordinates.
According to this embodiment, in the rotational center coordinate calculating step, the current rotational center coordinates that are the rotational center coordinates of the measuring surface of the measuring plate in the absolute space at present is calculated based on the caster angle detected in the caster angle detecting step and the mark coordinates detected in the mark coordinate detecting step. Thus, the rotational center position of the wheel can be detected real time without adjusting the rotational center of the measuring plate beforehand, and accurate wheel alignment measurements can be taken.
Also, there is no need to provide the measuring plate with a jig for adjusting the rotational center. This reduces the thickness of the measuring plate in the transverse direction of the vehicle being measured. Thus, the rotational radius at the time of a two angle change of the wheel can be reduced, and the area of the measuring surface of the measuring plate can be effectively utilized.
In a preferred embodiment of the present invention the rotational center coordinate calculating step comprises: a real mark coordinate calculating step of calculating reference mark coordinates which are the current coordinates of an initial mark coordinate, i.e., the coordinates of the rotational center specifying mark predetermined with the origin being initial rotational center coordinates corresponding to the initial values of the rotational center coordinates, based on the caster angle and the mark coordinates; and a current center coordinate calculating step of calculating the current rotational center coordinates.
According to this embodiment, in the real mark coordinate calculating step, the reference mark coordinates that are the current coordinates of the initial mark coordinates as the coordinates of the rotational center specifying mark predetermined with the origin being the initial rotational center coordinates, which are the initial value of the rotational center coordinates, are calculated based on the caster angle and the mark coordinates. In the current center coordinate calculating step, the current rotational center coordinates are calculated based on the reference mark coordinates obtained in the real mark coordinate calculating step. Thus, the rotational center position of the wheel can be quickly calculated from only a small amount of data.
In a preferred embodiment of the present invention the reference mark coordinates are calculated in the real mark coordinate calculating step using formulas (1) and (2):
X0xe2x80x3=X0xe2x80x2 cos(xcex8CAS)+Z0xe2x80x2 sin(xcex8CAS)xe2x80x83xe2x80x83(1)
Z0xe2x80x3=xe2x88x92X0xe2x80x2 sin(xcex8CAS)+Z0xe2x80x2 cos(xcex8CAS)xe2x80x83xe2x80x83(2)
and the current rotational center coordinates (X0, Z0) are calculated in the current center coordinate calculating step using formulas (3) and (4):
X0=X0xe2x80x2xe2x88x92X00+XXxe2x80x83xe2x80x83(3)
Z0=Z0xe2x80x3xe2x88x92Z00+ZZxe2x80x83xe2x80x83(4)
where the caster angle measured counterclockwise is xcex8CAS, the mark coordinates are (X0xe2x80x2, Z0xe2x80x2), the reference mark coordinates are (X0xe2x80x3, Z0xe2x80x3), the initial mark coordinates are (X00, Z00), and the initial rotational center coordinates are (XX, ZZ).
According to this embodiment, the reference mark coordinates are calculated using the formulas (1) and (2) in the real mark coordinate calculating step, and the current center coordinates (X0, Z0) are calculated using the formulas (3) and (4) in the current center coordinate calculating step . Thus, the rotational center position can be calculated by simple arithmetic operations, and real time processing can be performed without complicating the control operation by the arithmetic operation unit.
To achieve the second object, the present invention provides a measuring plate attached to a wheel of a vehicle being measured so that the origin corresponds to the rotational center of the wheel. This measuring plate comprises: a measuring mark area which formed in an area surrounding and containing the origin, and provided with various types of measuring marks; and a distance measuring area which is optically uniform and exposed to distance measuring light from the outside, and extends in the longitudinal direction of the vehicle being measured.
According to this embodiment, the measuring plate is provided with the optically uniform distance measuring area in the longitudinal direction of the vehicle being measured. Thus, by emitting the distance measuring light onto the distance measuring area, the distance from the measuring plate can be accurately measured, thereby improving the accuracy in wheel alignment measurement.
Since the distance measuring area can be large, an external distance measuring light emitting unit can be used on a fixed state. Thus, the structure of the wheel alignment measuring device can be simplified without reducing the measuring accuracy.
In a preferred embodiment of the present invention the distance measuring area extends in the longitudinal direction of the wheel of the vehicle being measured.
According to this embodiment, as the distance measuring area is formed in the longitudinal direction of the wheel of the vehicle being measured, two rays of the distance measuring light can be emitted onto two positions further apart in the longitudinal direction of the wheel. Thus, the angle measurement of the measuring plate can be made with high precision by calculating the difference between the lengths from the irradiation points of the two rays of the distance measuring light, and the accuracy in wheel alignment measurement can be further improved.
In a preferred embodiment of the present invention the measuring mark area contains: a first reference mark whose center coordinates are the origin of the measuring plate; a plurality of second reference marks whose center coordinates are at the intersections of first virtual lines and second virtual lines, the first virtual lines being in parallel with each other, and the second virtual lines being in parallel with each other and perpendicular to the first virtual lines; and a plurality of correction lines which are in parallel with either the first virtual lines or the second virtual lines, and are situated at fixed intervals.
According to this embodiment, since the first reference mark, the second reference marks, and the correction lines are drawn in the distance measuring mark area. Thus, various types of wheel alignment measurements can be taken speedily and accurately by picking up an image of the distance measuring mark area and performing image processing.
In a preferred embodiment of the present invention the wheel alignment measuring device comprises: at least two distance measuring units which are fixed in predetermined reference positions at a predetermined distance from each other, and emit the distance measuring light to output distance measuring signals corresponding to the distances from the measuring plate; and a distance calculating unit for calculating the distance from a predetermined position on the measuring plate corresponding to a predetermined reference position, based on the distance measuring signals.
According to this embodiment, the distance measuring units are fixed in the predetermined reference positions, emit the distance measuring light, and output the distance measuring signals corresponding to the distances from the measuring plate. The distance calculating unit calculates the distance from the predetermined position on the measuring plate corresponding to the reference position based on the distance measuring signals. In this embodiment, there is no need to employ a driving mechanism for driving the distance calculating unit, which simplifies the structure of the wheel alignment measuring device. Thus, the distance measuring accuracy, as well as the measuring plate angle measuring accuracy, can be maintained high.
To achieve the third object, the present invention provides a wheel alignment measuring device for measuring the distance from and the inclination of the measuring surface of a measuring plate which is attached to a wheel of a vehicle being measured so that the origin thereof corresponds to the center of the rotational axis of the wheel. This wheel alignment measuring device comprises four or more (number N) distance measuring light emitting and receiving units which emit distance measuring light onto the measuring surface, receive the distance measuring light reflected by the measuring surface, and output distance measuring signals. Emitters of the distance measuring light are arranged on the same virtual plate at fixed intervals, so that the distance measuring light of at least three of the N distance measuring light emitting and receiving units can be emitted onto the measuring surface under predetermined measuring conditions.
According to this embodiment, the distance measuring light is emitted onto the measuring surface by at least three distance measuring light emitting and receiving units under the predetermined measuring conditions, and the N distance measuring light emitting and receiving units receive the distance measuring light reflected by the distance measuring surface, thereby outputting the distance measuring signals. In this embodiment, measurements can be taken, with the distance measuring light emitting and receiving units being fixed, and there is no need to employ with a driving mechanism for driving the distance measuring light emitting and receiving units. Thus, the structure and the control operation can be simplified, and the device manufacturing cost can be reduced accordingly.
In a preferred embodiment of the present invention the virtual plane contains a straight line substantially in parallel with the vertical direction of the vehicle being measured, and a virtual parallelogram is arranged on the virtual plane so that the straight line includes one of the diagonal lines of the virtual parallelogram. The emitters of four of the distance measuring light emitting and receiving units are arranged at the comers of the virtual parallelogram, and the virtual parallelogram is arranged so that the distance measuring light is emitted from the emitters on the diagonal line not included in the straight line within the common area between a first measuring surface corresponding to the measuring surface moved the longest possible distance in a first direction along the straight line, and a second measuring surface corresponding to the measuring surface moved the longest possible distance in a second direction opposite from the first direction.
According to this embodiment, the distance measuring light is emitted on the measuring surface by at least three distance measuring light emitting units, which include one of the distance measuring light emitting unit on the diagonal line included in the straight line and the two distance measuring light emitting units on the other diagonal line. With the three distance measuring light emitters, accurate wheel alignment measurements can be constantly taken.
In a preferred embodiment of the present invention the wheel alignment measuring device further comprises: a choosing unit for choosing the distance measuring signal of the distance measuring light emitting and receiving unit corresponding to the emitter, which emits the distance measuring light upon the measuring surface, between the two emitters on the diagonal line included in the straight line; and a camber angle calculating unit for calculating the camber angle of the measuring surface based on the distance measuring signal chosen by the choosing unit, and distance measuring signals of the distance measuring light emitting and receiving units corresponding to the two emitters on the diagonal line not included in the straight line.
According to this embodiment, the choosing unit chooses the distance measuring signal of a distance measuring light emitting and receiving unit corresponding to the emitter, which emits the distance measuring light upon the measuring surface, between the two emitters on the diagonal line included in the straight line. The camber angle calculating unit calculates the camber angle of the measuring surface based on the distance measuring signal chosen by the choosing unit and the distance measuring signals of the distance measuring light emitting and receiving units corresponding to the emitters on the other diagonal line not included in the straight line. Thus, the camber angle can be accurately calculated along with displacement of the measuring plate, without a driving mechanism for driving the distance measuring light emitting and receiving units. Also, the distance between the distance measuring light emitting and receiving units included in the straight line and the other distance measuring light emitting and receiving units not included in the straight line can be made longer, thereby improving the accuracy of the camber angle measurement.
The camber angle calculating unit calculates the camber angle of the measuring surface based on the distance measuring signal chosen by the choosing unit and the distance measuring signals of the distance measuring light emitting and receiving units corresponding to the two emitters on the other diagonal line not included in the straight line.
In a preferred embodiment of the present invention the choosing unit comprises a judging unit for judging whether the intersection of the two diagonal lines is situated in the first direction or in the second direction with respect to the origin of the measuring surface, thereby choosing the corresponding distance measuring light emitting and receiving unit.
According to this embodiment, the judging unit of the choosing unit judges whether the intersection of the two diagonal lines is situated in the first direction or in the second direction with respect to the origin of the measuring surface, thereby choosing the corresponding distance measuring light emitting and receiving unit. Thus, the distance measuring light emitting and receiving unit to be used in the camber angle calculation can be quickly selected, and the camber angle can be calculated speedily and accurately.
In a preferred embodiment of the present invention the wheel alignment measuring method comprising: a distance measuring light emitting and receiving step in which at least three rays of distance measuring light among N (N=4 or larger) rays of distance measuring light are emitted onto the measuring surface at predetermined intervals; and a camber angle calculating step of calculating the camber angle of the measuring surface based on the received distance measuring light.
According to this embodiment, in the distance measuring light emitting and receiving step, at least three rays of distance measuring light among N (N=4 or larger) rays of distance measuring light are emitted onto the measuring surface at predetermined intervals. In the camber angle calculating step, the camber angle of the measuring surface is calculated based on the receiving distance measuring light. Since no driving control needs to be performed to conform to the displacement of the measuring surface, the control procedure can be simplified, and the cost for control system development can be lowered.
In a preferred embodiment of the present invention a virtual plane contains a straight line substantially in parallel with the vertical direction of the vehicle being measured. Also, a virtual parallelogram is arranged on the virtual plane so that the straight line contains one of the diagonal lines of the virtual parallelogram, and the distance measuring light is emitted from each corner of the virtual parallelogram and the distance measuring light reflected by the measuring surface is received in the distance measuring light emitting and receiving step. The distance measuring light emitted from two corners on the diagonal line not included in the straight line and from one of the comers on the diagonal line included in the straight line is received in the common area between a first measuring surface corresponding to the measuring surface moved the longest possible distance in a first direction along the straight line, and a second measuring surface corresponding to the measuring surface moved the longest possible distance in a second direction opposite from the first direction, thereby calculating the camber angle in the camber angle calculating step.
According to this embodiment, in the distance measuring light emitting and receiving step, the distance measuring light is emitted from each comer of the virtual parallelogram, and the distance measuring light reflected by the measuring surface is received. In the camber angle calculating step, the camber angle is calculated based on the received distance measuring light emitted from the two comers on the diagonal line not included in the straight lint included in the common area between the first measuring surface and the second measuring surface, and the received distance measuring light emitted from one of the comers on the other diagonal line. Thus, the camber angle can be accurately calculated in accordance with displacement of the measuring surface.
In a preferred embodiment of the present invention the camber angle calculating step comprises: a choosing step of choosing a ray of distance measuring light irradiating the measuring surface between the two rays of distance measuring light emitted from the corners included in the straight line; and a camber angle operation step of calculating the camber angle of the measuring surface based on the distance measuring light chosen in the choosing step and the two rays of distance measuring light emitted from the comers not included in the straight line.
According to this embodiment, in the choosing step, a ray of distance measuring light irradiating the measuring surface is chosen between the two rays of distance measuring light emitted from the comers included in the straight line. In the camber angle operation step, the camber angle of the measuring surface is calculated based on the distance measuring light chosen in the choosing step and the two rays of distance measuring light emitted from the comers not included in the straight line. In this embodiment, the camber angle can be accurately calculated in accordance with displacement of the measuring plate, and the length of the measuring light emitted from the two comers not included in the straight line can be made longer with respect to the distance measuring light emitted from one of the comers included in the straight line. Thus, the accuracy in the camber angle calculation can be improved.
In a preferred embodiment of the present invention the choosing step comprises a judging step of judging whether the intersection of the two diagonal lines is situated in the first direction or in the second direction with respect to the origin of the measuring surface, thereby choosing the corresponding distance measuring light.
According to this embodiment, in the judging step, the distance measuring light is chosen by judging whether the intersection of the two diagonal lines is situated in the first direction or in the second direction with respect to the origin of the measuring surface. Thus, the distance measuring light can be chosen quickly, and the camber angle can be calculated speedily and accurately.
To achieve the fourth object, the present invention provides a caster angle measuring device for outputting effective caster angle data xcex8ECAS having a desired measuring accuracy based on image data obtained through image pick-up, by an external CCD camera, of a caster angle measuring object line drawn on a wheel alignment measuring target plate provided to a vehicle. This caster angle measuring device comprises: an original caster angle data calculating unit for calculating original caster angle data xcex8CAS by quantizing the caster angle formed by the measuring object line with respect to a predetermined reference line based on the image data; and an effective data output unit for outputting the original caster angle data xcex8CAS as the effective caster angle data xcex8ECAS when the original caster angle data xcex8CAS change in value.
According to this embodiment, the original caster angle data calculating unit calculates the original caster angle data xcex8CAS by quantizing the caster angle formed by the measuring object line with respect to the predetermined reference line based on the image data outputted by the external CCD camera. The effective data output unit outputs the original caster angle data xcex8CAS as the effective caster angle data xcex8ECAS when the original caster angle data xcex8CAS change in value. Although the caster angle is optically calculated in a non-contact manner using the image data outputted by the CCD camera, the measuring accuracy in measuring the caster angle can be maintained at a desired level. Thus, with the effective caster angle data xcex8ECAS, the wheel alignment can be quickly measured with a desired accuracy.
In a preferred embodiment of the present invention a caster angle measuring device is provided for outputting effective caster angle data xcex8ECAS having a desired measuring accuracy based on image data obtained through image pick-up, by an external CCD camera, of a caster angle measuring object line drawn on a wheel alignment measuring target plate provided to a vehicle. This caster angle measuring device comprises: an original caster angle data calculating unit for calculating original caster angle data xcex8CAS based on the image data when the caster angle formed by the measuring object line with respect to a predetermined reference line constantly increases or decreases; a comparator comparing original caster angle data xcex8CAS(nxe2x88x921) in the previous measurement with original caster angle data xcex8CAS(n) in the current measurement; and an effective data output unit for outputting the original caster angle data xcex8CAS(n) of the current measurement as the effective caster angle data xcex8ECAS when the previous original caster angle data xcex8CAS(nxe2x88x921) is not equal to the current original caster angle data xcex8CAS(n) as a result of the comparison.
According to this embodiment, the original caster angle data calculating unit calculates the original caster angle data xcex8CAS based on the image data when the caster angle formed by the measuring object line with respect to the predetermined reference line constantly increases or decreases. The comparator compares the original caster angle data xcex8CAS(nxe2x88x921) in the previous measurement with the original caster angle data xcex8CAS(n) in the current measurement. The effective data output unit outputs the original caster angle data xcex8CAS(n) of the current measurement as the effective caster angle data xcex8ECAS when the previous original caster angle data xcex8CAS(nxe2x88x921) is not equal to the current original caster angle data xcex8CAS(n) as a result of the comparison. Although the caster angle is calculated in a non-contact manner using the image data outputted by the CCD camera, the measuring accuracy in measuring the caster angle can be maintained at a desired level. Thus, with the effective caster angle data xcex8ECAS, the wheel alignment can be quickly measured with a desired accuracy.
In a preferred embodiment of the present invention the original caster angle data calculating unit comprises: a line extracting unit for extracting the measuring object line based on the image data; and an inclination calculating unit for calculating the inclination of the extracted measuring object line by the method of least squares.
According to this embodiment, the line extracting unit extracts the measuring object line based on the image data, and the inclination calculating unit calculates the inclination of the extracted measuring object line by the method of least squares. Thus, the effective caster angle data xcex8ECAS can be calculated speedily and accurately.
In a preferred embodiment of the present invention the original caster angle data calculating unit comprises: a line extracting unit for extracting the measuring object line based on the image data; and an inclination calculating unit for calculating the inclination of the extracted measuring object line by the method of least squares.
According to this embodiment, the line extracting unit extracts the measuring object line based on the image data, and the inclination calculating unit calculates the inclination of the extracted measuring object line by the method of least squares. Thus, the effective caster angle data xcex8ECAS can be calculated speedily and accurately.
In a preferred embodiment of the present invention the wheel alignment measuring device comprises: a CCD camera for outputting image data by picking up an image of a caster angle measuring object line drawn on a wheel alignment measuring target plate attached to a vehicle; the caster angle measuring device; and a data comparing unit for comparing the effective caster angle data xcex8ECAS with measuring data of another dimension measured at substantially the same time that a change occurs to the original caster angle data xcex8CAS.
According to this embodiment, the CCD camera picks up an image of the caster angle measuring object line drawn on the wheel alignment measuring target plate attached to the vehicle, and outputs the image data to the caster angle measuring device. The caster angle measuring device outputs the effective caster angle data xcex8ECAS to the data comparing unit. The data comparing unit compares the effective caster angle data xcex8ECAS with measuring data of another dimension measured at substantially the same time that a change occurs to the original caster angle data xcex8CAS. Thus, various data in wheel alignment measurement can be compared with the caster angle data with a desired accuracy.
In a preferred embodiment of the present invention the wheel alignment measuring device comprises: a CCD camera for outputting image data by picking up an image of a caster angle measuring object line drawn on a wheel alignment measuring target plate attached to a vehicle; the caster angle measuring device; and a data comparing unit for comparing the current original caster angle data xcex8CAS(n) with measuring data of another dimension measured at substantially the same time as the measurement of the current original caster angle data xcex8CAS(n).
According to this embodiment, the CCD camera picks up an image of the caster angle measuring object line drawn on the wheel alignment measuring target plate attached to the vehicle, and outputs the image data to the caster angle measuring device. The caster angle measuring device outputs the current original caster angle data xcex8CAS(n) as the effective caster angle data xcex8ECAS to the data comparing unit. The data comparing unit compares the current original caster angle data xcex8CAS(n) with measuring data of another dimension measured at substantially the same time as the measurement of the current original caster angle data xcex8CAS(n). Thus, various data in wheel alignment measurement can be compared with the caster angle data with a desired accuracy.
In a preferred embodiment of the present invention the caster angle measuring method for calculating an effective caster angle xcex8ECAS having a desired measuring accuracy based on image data is obtained through image pick-up, by an external CCD camera, of a caster angle measuring object line drawn on a wheel alignment measuring target plate attached to a vehicle. This caster angle measuring method comprises: an original caster angle calculating step of calculating an original caster angle xcex8CAS by quantizing the caster angle formed by the measuring object line with respect to a predetermined reference line based on the image data; and an effective data judging step for judging the original caster angle xcex8CAS at the time of a change in value thereof to be the effective caster angle xcex8ECAS.
According to this embodiment, in the original caster angle calculating step, the original caster angle xcex8CAS is calculated by quantizing the caster angle formed by the measuring object line with respect to the predetermined reference line based on the image data. In the effective data judging step, the original caster angle xcex8CAS at the time of a change in value thereof is judged to be the effective caster angle xcex8ECAS. Although the caster angle is calculated in a non-contact manner using the image data outputted by the CCD camera, the measuring accuracy in measuring the caster angle can be maintained at a desired level. Thus, with the effective caster angle data xcex8ECAS, the wheel alignment can be quickly measured with a desired accuracy.
In a preferred embodiment of the present invention the caster angle measuring method for calculating an effective caster angle xcex8ECAS having a desired measuring accuracy based on image data is obtained through image pick-up, by an external CCD camera, of a caster angle measuring object line drawn on a wheel alignment measuring target plate attached to a vehicle. This caster angle measuring method comprises: an original caster angle calculating step of calculating an original caster angle xcex8CAS based on the image data when the caster angle formed by the measuring object line with respect to a predetermined reference line constantly increases or decreases; a comparing step of comparing an original caster angle xcex8CAS(nxe2x88x921) in the previous measurement with an original caster angle xcex8CAS(n) in the current measurement; and an effective data judging step of judging the current original caster angle xcex8CAS(n) to be the effective caster angle xcex8ECAS when the previous original caster angle xcex8CAS(nxe2x88x921) is not equal to the current original caster angle xcex8CAS(n) as a result of the comparison.
According to this embodiment, in the original caster angle calculating step, the original caster angle xcex8CAS is calculated based on the image data when the caster angle formed by the measuring object line with respect to the predetermined reference line constantly increases or decreases. In the comparing step, the original caster angle xcex8CAS(nxe2x88x921) in the previous measurement is compared with the original caster angle xcex8CAS(n) in the current measurement. In the effective data judging step, the current original caster angle xcex8CAS(n) is judged to be the effective caster angle xcex8ECAS when the previous original caster angle xcex8CAS(nxe2x88x921) is not equal to the current original caster angle xcex8CAS(n) as a result of the comparison. Although the caster angle is calculated in a non-contact manner using the image data outputted by the CCD camera, the measuring accuracy in measuring the caster angle can be maintained at a desired level. Thus, with the effective caster angle data xcex8ECAS, the wheel alignment can be quickly measured with a desired accuracy.
In a preferred embodiment of the present invention the original caster angle calculating step comprises: a line extracting step of extracting the measuring object line based on the image data; and an inclination calculating step of calculating-the inclination of the measuring object line extracted by the method of least squares.
According to this embodiment, in the line extracting step, the measuring object line is extracted based on the image data. In the inclination calculating step, the inclination of the extracted measuring object line is calculated by the method of least squares. Thus, the effective caster angle data xcex8ECAS can be calculated speedily and accurately.
In a preferred embodiment of the present invention the original caster angle calculating step comprises: a line extracting step of extracting the measuring object line based on the image data; and an inclination calculating step of calculating the inclination of the measuring object line extracted by the method of least squares.
According to this embodiment, in the line extracting step, the measuring object line is extracted based on the image data. In the inclination calculating step, the inclination of the extracted measuring object line is calculated by the method of least squares. Thus, the effective caster angle data xcex8ECAS can be calculated speedily and accurately.
In a preferred embodiment of the present invention the wheel alignment measuring method comprises: an image pick-up step of picking up an image of a caster angle measuring object line drawn on a wheel alignment measuring target plate attached to a vehicle; an original caster angle calculating step of calculating an original caster angle xcex8CAS by quantizing the caster angle formed by the picked-up measuring object line with respect to a predetermined reference line; an effective data judging step of judging the original caster angle xcex8CAS at the time of a change in value thereof to be effective caster angle xcex8ECAS; and a data comparing step of comparing the effective caster angle xcex8ECAS with measuring data of another dimension at substantially the same time that there is a change in the original caster angle xcex8CAS.
According to this embodiment, in the image pick-up step, an image of the caster angel measuring object line drawn on the wheel alignment measuring target plate attached to the vehicle is picked up. In the original caster angle calculating step, the original caster angle xcex8CAS is calculated by quantizing the caster angle formed by the picked-up measuring object line with respect to the predetermined reference line. In the effective data judging step, the original caster angle xcex8CAS at the time of a change in value thereof is judged to be the effective caster angle xcex8ECAS. In the data comparing step, the effective caster angle xcex8ECAS is compared with the measuring data of another dimension at substantially the same time that there is a change in the original caster angle xcex8CAS. Thus, various data in wheel alignment measurement can be compared with the caster angle data with a desired accuracy.
In a preferred embodiment of the present invention the wheel alignment measuring method comprises: an image pick-up step of picking up an image of a caster angle measuring object line drawn on a wheel alignment measuring target plate attached to a vehicle; an original caster angle calculating step of calculating an original caster angle when the caster angle formed by the picked-up measuring object line with respect to a predetermined reference line constantly increases or decreases; a comparing step of comparing an original caster angle xcex8CAS(nxe2x88x921) in the previous measurement with an original caster angle xcex8CAS(n) in the current measurement; an effective data judging step of judging the current original caster angle xcex8CAS(n) to be effective caster angle xcex8ECAS when the previous original caster angle xcex8CAS(nxe2x88x921) is not equal to the current original caster angle xcex8CAS(n) as a result of the comparison; and a data comparing step of comparing the current original caster angle xcex8CAS(n) with measuring data of another dimension measured at substantially the same time as the measurement of the current original caster angle xcex8CAS(n).
According to this embodiment, in the image pick-up step, an image of the caster angle measuring object line drawn on the wheel alignment measuring target plate attached to the vehicle is picked up. In the original caster angle calculating step, the original caster angle is calculated when the caster angle formed by the picked-up measuring object line with respect to the predetermined reference line constantly increases or decreases. In the comparing step, the original caster angle xcex8CAS(nxe2x88x921) in the previous measurement is compared with the original caster angle xcex8CAS(n) in the current measurement. In the effective data judging step, the current original caster angle xcex8CAS(n) is judged to be the effective caster angle xcex8ECAS when the previous original caster angle xcex8CAS(nxe2x88x921) is not equal to the current original caster angle xcex8CAS(n) as a result of the comparison. In the data comparing step, the current original caster angle xcex8CAS(n) is compared with the measuring data of another dimension measured at substantially the same time as the measurement of the current original caster angle xcex8CAS(n). Thus, various data in wheel alignment measurement can be compared with the caster angle data with a desired accuracy.
To achieve the fifth object, the present invention provides a measuring plate characterized by a measuring surface on which are drawn: a first reference mark whose center coordinates are situated at a predetermined origin; a plurality of second reference marks each having center coordinates situated at the intersections of first virtual lines and second virtual lines; and a plurality of correction lines which are in parallel with either the first virtual lines or the second virtual lines and situated at fixed intervals. The first virtual lines are in parallel with each other, and the second virtual lines are perpendicular to the first virtual lines and in parallel with each other. The predetermined origin corresponds to the center of the rotational axis of a wheel of a vehicle being measured.
According to this embodiment, the first reference mark, the second reference marks, and the correction lines are drawn on the measuring surface of the measuring plate. The center coordinates of the first reference mark are situated at the predetermined origin. The center coordinates of each second reference mark are situated at the intersection of a first virtual line and a second virtual line. The measuring plate is attached to the wheel of the vehicle so that the origin corresponds to the center of the rotational axis of the wheel. Any position on the picked-up image can be easily detected in the relative positional relationship with the center of the rotational axis of the wheel of the measured vehicle, and displacement (suspension properties or wheel alignment properties) of the rotational axis of the wheel can be measured at high speed in a large area of a three dimensional space in a constant and non-contact manner. Also, the position coordinates can be calculated with accuracy based on the second pick-up signal, regardless of the position of the measuring plate.
In a preferred embodiment of the measuring plate the first reference mark, the second reference marks, and the correction lines are in different colors from each other.
In this embodiment, the first reference mark, the second reference marks, and the correction lines are in different colors from each other. Thus, they are easily distinguishable in image processing of the picked-up image, and measurements can be taken speedily and accurately.
In a preferred embodiment of the measuring plate the first reference mark and the second reference marks are colored red, green, or blue.
According to this embodiment, the first reference mark and the second reference marks are colored red, green, or blue. By performing color separation in image processing, the reference marks can be easily and quickly distinguished without requiring complicated data processing.
In a preferred embodiment of the measuring plate the remaining area on the measuring surface, except for the first reference mark, the second reference marks, and the correction lines, is a base area which is colored black or white. The correction lines are colored black or white, whichever is different from the base area.
According to this embodiment, the base area is colored black or white, and the correction lines are black or white, whichever is different from the color of the base area. Thus, the correction lines can be easily distinguished by binary processing, and the image processing can be performed at high speed, which enables accurate wheel alignment measurement.
In a preferred embodiment of the measuring plate the first reference mark is painted in a different color from the color of a vehicle being measured.
According to this embodiment, the first reference mark is painted in a different color from the color of the vehicle, so that the color of the vehicle will not be mistaken for the first reference mark. Thus, accurate measurements can be taken.
In a preferred embodiment of the present invention the wheel alignment measuring device for measuring wheel alignment using the measuring plate comprises: a first image pick-up unit for outputting a first picked-up image signal by picking up an image of a first area including the first reference mark and the second reference marks on the measuring surface of the measuring plate; a second image pick-up unit for outputting a second picked-up image signal by picking up an image of a second area smaller than the first area and included in the first area, the second image pick-up unit having an optical axis situated in a position predetermined with respect to the optical axis of the first image pick-up unit; a selecting unit for selecting one of the second reference marks included in the second area based on the second picked-up image signal; a relative reference position calculating unit for calculating the position coordinates of the selected second reference mark as relative reference position coordinates after specifying the selected second reference mark within the first area based on the first picked-up image signal; and a position calculating unit for calculating origin reference position coordinates which are the position coordinates of the origin in a predetermined position within the second area based on the second picked-up image signal and the relative reference position coordinates.
According to this embodiment, the first image pick-up unit outputs the first picked-up image signal to the relative reference position calculating unit by picking up an image of the first area including the first reference mark and the second reference marks on the measuring surface of the measuring plate. The second image pick-up unit outputs the second picked-up image signal to the selecting unit and the position calculating unit by picking up an image of the second area smaller than the first area and included in the first area. The selecting unit selects one of the second reference marks included in the second area based on the second picked-up image signal. The relative reference position calculating unit specifies the selected second reference mark within the first area based on the first picked-up image signal, and calculates the position coordinates of the selected second reference mark as the relative reference position coordinates. The position calculating unit calculates the origin reference position coordinates which are the position coordinates of the origin in the predetermined position within the second area based on the second picked-up image signal and the relative reference position coordinates. Thus, the wheel alignment can be constantly and highly accurately measured in a large area in a three dimensional space in a non-contact manner.
In a preferred embodiment of the present invention the selecting unit selects a second reference mark which is the closest to the predetermined position in the second area.
According to this embodiment, the selecting unit selects a second reference mark which is the closest to the predetermined position in the second area. Thus, the original position reference position coordinates can be calculated with a smaller error, and the wheel alignment can be measured more accurately.
In a preferred embodiment of the present invention the wheel alignment measuring device further comprises a color separation unit which receives the first picked-up image signal and the second picked-up image signal, performs color separation, and outputs a first color separation picked-up image signal consisting of a first red picked-up image signal, a first green picked-up image signal, and a first blue picked-up image signal, and a second color separation picked-up image signal consisting of a second red picked-up image signal, a second green picked-up image signal, and a second blue picked-up image signal. The selecting unit specifies the selected second reference mark based on the second color separation picked-up image signal, and the relative reference position calculating unit calculates the relative reference position coordinates based on the first color separation picked-up image signal.
According to this embodiment, the color separation unit receives the first picked-up image signal and the second picked-up image signal, performs color separation, and then outputs the first color separation picked-up image signal consisting of the first red picked-up image signal, the first green picked-up image signal, and the first blue picked-up image signal, and the second red picked-up image signal, the second green picked-up image signal, and the second blue picked-up image signal. The selecting unit specifies the selected second reference mark based on the second color separation picked-up image signal. The relative reference position calculating unit calculates the relative reference position coordinates based on the first color separation picked-up image signal. Thus, the image processing can be simplified, and the wheel alignment can be measured at high speed.
In a preferred embodiment of the present invention the wheel alignment measuring device further comprises a color separation unit which receives the first picked-up image signal and the second picked-up image signal, performs color separation, and outputs a first color separation picked-up image signal consisting of a first red picked-up image signal, a first green picked-up image signal, and a first blue picked-up image signal, and a second color separation picked-up image signal consisting of a second red picked-up image signal, a second green picked-up image signal, and a second blue picked-up image signal. The selecting unit specifies the selected second reference mark based on the second color separation picked-up image signal, and the relative reference position calculating unit calculates the relative reference position coordinates based on the first color separation picked-up image signal.
According to this embodiment, the color separation unit receives the first picked-up image signal and the second picked-up image signal, and performs color separation. The color separation unit then outputs the first color separation picked-up image signal consisting of the first red picked-up image signal, the first green picked-up image signal, and the first blue picked-up image signal to the relative reference position calculating unit, and the second color separation picked-up image signal consisting of the second red picked-up image signal, the second green picked-up image signal, and the second blue picked-up image signal to the selecting unit.
The selecting unit specifies the selected second reference mark based on the second color separation picked-up image signal, and the relative reference position calculating unit calculates the relative reference position coordinates based on the first color separation picked-up image signal.
In a preferred embodiment of the present invention the relative reference position calculating unit comprises a center position calculating unit which calculates the center position coordinates of the selected second reference mark as the relative reference position coordinates based on the second color separation picked-up image signal. The position calculating unit comprises: a relative position coordinate calculating unit for calculating the relative position coordinates of the predetermined position relative to the relative reference position coordinates; and an origin reference position coordinate calculating unit for calculating the origin position reference position coordinates by adding the relative position coordinates to the center position coordinates of the selected second reference mark.
According to this embodiment, the center position calculating unit of the relative reference position calculating unit calculates the center position coordinates of the selected second reference mark as the relative reference position coordinates based on the second color separation picked-up image signal. The relative position coordinate calculating unit calculates the relative position coordinates of the predetermined position relative to the relative reference position coordinates. The origin reference position coordinate calculating unit calculates the origin position reference position coordinates by adding the relative position coordinates to the center position coordinates of the selected second reference mark. Thus, the center position of the selected second reference mark, i.e., the wheel alignment of the vehicle, can be quickly measured with a high accuracy based on the second picked-up image.
In a preferred embodiment of the present invention the wheel alignment measuring device further comprises: a plurality of distance sensors which measure the distances from different positions on the measuring surface of the measuring plate, and outputs measuring signals; and a distance calculating unit for calculating the distance from the measuring surface and the camber angle based on the measuring signals from the plurality of distance sensors.
According to this embodiment, the distance calculating unit calculates the distance from the measuring surface based on the measuring signals outputted from the plurality of the distance sensors that measure the distances from different positions on the measuring surface of the measuring plate. Thus, the distance from the measuring surface and the camber angle can be calculated speedily and accurately.
In a preferred embodiment of the present invention the wheel alignment measuring method comprises: a first image picked-up step of picking up an image of a first area containing the first reference mark and the second reference marks on the measuring surface of the measuring plate; a second image pick-up step of picking up an image of a second area smaller than the first area and included in the second area; a selecting step of selecting one of the second reference marks included within the second area as a selected second reference mark; a relative reference position calculating step of calculating relative reference position coordinates which are the position coordinates of the selected second reference mark specified in the first area; and a position calculating step of calculating origin position reference position coordinates which are the position coordinates of the origin of a predetermined position in the second area, based on the relative reference position coordinates.
According to this embodiment, in the first image pick-up step, an image of the first area containing the first reference mark and the second reference marks on the measuring surface of the measuring plate is picked up. In the second image pick-up step, an image of the second area smaller than the first area and included in the second area is picked up. In the selecting step, one of the second reference marks included within the second area is selected as the selected second reference mark. In the relative reference position calculating step, the relative reference position coordinates, which are the position coordinates of the selected second reference mark specified in the first area, are calculated. In the position calculating step, the origin position reference position coordinates, which are the position coordinates of the origin of the predetermined position in the second area, are calculated based on the relative reference position coordinates. Thus, the position of any point on the picked-up image can be detected in relation with the center of the rotational axis of the wheel of the vehicle being measured, and displacement (suspension properties or wheel alignment properties) of the rotational axis of the wheel is constantly measured at speed in a large area in a three-dimensional space in a non-contact manner. Also, the position coordinates can be calculated with accuracy based on the second picked-up image signal, regardless of the position of the measuring plate.
In a preferred embodiment of the present invention the selected second reference mark is the second reference mark closest to the predetermined position among the second reference marks in the second area in the selecting step.
According to this embodiment, in the selecting step, the second reference mark closest to the predetermined position is selected as the selected second reference mark among the second reference marks in the second area. Thus, the origin position reference position coordinates can be calculated with a smaller error.
In a preferred embodiment of the present invention the wheel alignment measuring device further comprises a color separation step of performing color separation on the images picked up in the first image pick-up step and the second image pick-up step so as to generate a first color separation picked-up image and a second color separation picked-up image. In the selecting step, the selected second reference mark is specified based on the second color separation picked-up image. In the relative reference position calculating step, the relative reference position coordinates are calculated based on the first color separation picked-up image.
According to this embodiment, in the color separation step, color separation is performed on the images picked up in the first image pick-up step and the second image pick-up step so as to generate the first color separation picked-up image and the second color separation picked-up image. In the selecting step, the selected second reference mark is specified based on the second color separation picked-up image. In the relative reference position calculating step, the relative reference position coordinates are calculated based on the first color separation picked-up image. Thus, the image processing can be simplified, and the wheel alignment can be easily and quickly measured.
In a preferred embodiment of the present invention the relative reference position calculating step comprises a center position calculating step of calculating the relative reference position coordinates, which are the center position coordinates of the selected second reference mark, based on the second color separation picked-up image. Also, the position calculating step comprises: a relative position coordinate calculating step of calculating the relative position coordinates of the predetermined position with respect to the relative reference position coordinates; and an origin reference position coordinate calculating step of calculating the origin position reference position coordinates by adding the relative position coordinates to the center position coordinates of the selected second reference mark.
According to this embodiment, in the center position calculating step, the relative reference position coordinates, which are the center position coordinates of the selected second reference mark, are calculated based on the second color separation picked-up image. In the relative position coordinate calculating step, the relative position coordinates of the predetermined position with respect to the relative reference position coordinates are calculated. In the origin reference position coordinate calculating step, the origin position reference position coordinates are calculated by adding the relative position coordinates to the center position coordinates of the selected second reference mark. Thus, the center position of the selected second reference mark can be detected with a high accuracy based on the second picked-up image signal, and the wheel alignment of the vehicle can be speedily and highly accurately measured.
In a preferred embodiment of the present invention the wheel alignment measuring method further comprises: a distance measuring step of measuring the distances from different positions on the measuring surface of the measuring plate; and a distance calculating step of calculating the distance from the measuring surface and the camber angle based on the distances measured in the distance measuring step.
According to this embodiment, in the distance measuring step, the distances from different positions on the measuring surface of the measuring plate are measured. In the distance calculating step, the distance from the measuring surface and the camber angle are calculated based on the distances measured in the distance measuring step.
To achieve the sixth object, a preferred embodiment of the present invention provides a measuring plate characterized by having a measuring surface on which a plurality of concentric circles having a predetermined origin and grid scale lines are drawn, and being attached to a wheel of a vehicle being measured so that the origin corresponds to the center of the rotational axis of the wheel.
According to this embodiment, a plurality of concentric circles having the predetermined origin and grid scale lines are drawn on the measuring surface, and the position of the origin corresponds to the center of the rotational axis of the vehicle. A concentric circle whose image is picked up with the measuring plate is specified based on its curvature. The measuring object position relative to the rotational axis of the wheel can be speedily and accurately calculated based on the positional relationship between the concentric circle and the grid scale lines. Thus, the wheel alignment can be speedily and accurately measured, and the reproducibility and reliability of the measurement can be improved.
In a preferred embodiment of the present invention the scale lines comprise first scale lines in parallel with each other, and second scale lines perpendicular to the first scale lines and in parallel with each other, and the concentric circles and the first and second scale lines are drawn in different colors.
According to this embodiment, the concentric circles, the first scale lines, and the second scale lines are drawn in different colors, so that each of them can be easily distinguished, and that the measuring object position can be accurately detected.
In a preferred embodiment of the present invention the concentric circles and the first and second scale lines are colored red, green, or blue.
According to this embodiment, the concentric circles and the first and second scale lines are colored red, green, or blue, and color separation by three primary colors is performed to distinguish them. Thus, the positions can be speedily and accurately measured, and the wheel alignment can also be speedily and accurately measured.
In a preferred embodiment of the present invention the wheel alignment measuring device comprises: an image pick-up unit for picking up an image of the measuring surface so that at least a part of at least one of the concentric circles and at least a part of the scale lines are included in the picked-up image; a judging unit for judging which concentric circle is included in the image picked up by the image pick-up unit based on the curvature of the concentric circle in the picked-up image; a scale line specifying unit for specifying the scale lines included in the picked-up image based on the judgrnent made by the judging unit; and an operation unit for calculating the position on the measuring plate corresponding to a measuring object position, based on the positional relationship between the specified scale lines and the measuring object position in the image picked up by the image pick-up unit.
According to this embodiment, the image pick-up unit picks up an image of the measuring surface at least a part of at least one of the concentric circles and at least a part of the scale lines are included in the picked-up image. The judging unit judges which concentric circle is included in the image picked up by the image pick-up unit based on the curvature of the concentric circle in the picked-up image. The scale line specifying unit specifies the scale lines included in the picked-up image based on the judgment made by the judging unit. The operation unit calculates the position of the measuring plate corresponding to the measuring object position, based on the positional relationship between the specified scale lines and the measuring object position in the image picked up by the image pick-up unit. Thus, the position on the measuring plate corresponding to the measuring object position can be accurately calculated, and wheel alignment measurements of high reproducibility and reliability can be accurately taken.
In a preferred embodiment of the present invention the judging unit comprises: a storing unit for storing the curvatures of the concentric circles in advance; a concentric circle extracting unit for extracting a concentric circle contained in the picked-up image based on output signals from the image pick-up unit; a curvature calculating unit for calculating the curvature of the extracted concentric circle; and a concentric circle specifying unit for specifying the concentric circle by comparing the curvature obtained by the curvature calculating unit with the curvatures stored in the storing unit.
According to this embodiment, the storing unit stores the curvatures of the concentric circles, and the concentric circle extracting unit extracts the concentric circle included in the picked-up image based on the curvature of the concentric circle and the output signal of the image pick-up unit. The curvature calculating unit calculates the curvature of the extracted concentric circle, and the concentric circle specifying unit specifies the concentric circle by comparing the curvature obtained by the curvature calculating unit with the curvatures stored in the storing unit. Thus, the concentric circle can be surely and accurately specified, and the measuring object position can be accurately measured.
In a preferred embodiment of the present invention the wheel alignment measuring device comprises: an image pick-up unit for outputting picked-up image data by picking up an image of the measuring surface so that at least a part of at least one of the concentric circles and at least a part of the scale lines are included in the picked-up image; a color separation unit for outputting color separation picked-up image data by performing color separation on the picked-up image data; a judging unit for judging which concentric circle is included in the image picked up by the image pick-up unit based on the color separation picked-up image data and the curvature of the concentric circle in the picked-up image; a scale line specifying unit for specifying the scale lines included in the picked-up image based on the judgment made by the judging unit and the color separation picked-up image data; and an operation unit for calculating the position on the measuring plate corresponding to a measuring object position, based on the positional relationship between the specified scale lines and the measuring object position in the image picked up by the image pick-up unit.
According to this embodiment, the image pick-up unit picks up an image of the measuring surface so that at least a part of at least one of the concentric circles and at least a part of the scale lines are included in the picked-up image, and then outputs picked-up image data to the color separation unit. The color separation unit performs color separation on the picked-up image data, and outputs color separation picked-up image data to the judging unit. The judging unit judges which concentric circle is included in the image picked up by the image pick-up unit based on the color separation picked-up image data and the curvature of the concentric circle in the picked-up image. The scale line specifying unit specifies the scale lines included in the picked-up image based on the judgment made by the judging unit and the color separation picked-up image data. The operation unit calculates the position on the measuring plate corresponding to the measuring object position based on the positional relationship between the specified scale lines and the measuring object position in the image picked up by the image pick-up unit. Thus, the position on the measuring plate corresponding to the measuring object position can be speedily and accurately calculated, and as a result, accurate wheel alignment measurements of high reproducibility and reliability can be accurately taken.
In a preferred embodiment of the present invention the judging unit comprises: a storing unit for storing the curvatures of the concentric circles in advance; a concentric circle extracting unit for extracting a concentric circle included in the picked-up image based on the color separation picked-up image data; a curvature calculating unit for calculating the curvature of the extracted concentric circle; and a concentric circle specifying unit for specifying the concentric circle by comparing the curvature obtained by the curvature calculating unit with the curvatures stored in the storing unit.
According to this embodiment, the storing unit stores the curvatures of the concentric circles in advance, and the concentric extracting unit extracts the concentric circle included in the picked-up image based on the color separation picked-up image data The curvature calculating unit calculates the curvature of the extracted concentric circle, and the concentric circle specifying unit specifies the concentric circle by comparing the curvature obtained by the curvature calculating unit with the curvatures stored in the storing unit. Thus, the concentric circle can be specified speedily and accurately.
In a preferred embodiment of the present invention the wheel alignment measuring device further comprises a spin angle calculating unit for calculating a spin angle by determining the inclination of the scale lines included in the picked-up image with respect to a predetermined reference position.
According to this embodiment, the spin angle calculating unit calculates a spin angle by determining the inclination of the scale lines included in the picked-up image with respect to the predetermined reference position. Thus, the spin angle can be speedily and accurately calculated.
In a preferred embodiment of the present invention the wheel alignment measuring method comprises: an image pick-up step of picking up an image of the measuring surface so that at least a part of at least one concentric circles and at least a part of the scale lines are included in the picked-up image; a judging unit of judging which concentric circle is included in the picked-up image based on the curvature of the concentric circle included in the picked-up image; a scale line specifying step of specifying the scale lines included in the picked-up image based on the judgment made in the judging step; and an operation step of calculating the position on the measuring plate corresponding to a measuring object position, based on the positional relationship between the specified scale lines and the measuring object position in the picked-up image.
According to this embodiment, in the image pick-up step, an image of the measuring surface is picked up so that at least a part of at least one concentric circles and at least a part of the scale lines are included in the picked-up image. In the judging step, which concentric circle is included in the picked-up image is judged based on the curvature of the concentric circle included in the picked-up image. In the scale line specifying step, the scale lines included in the picked-up image are specified based on the judgment made in the judging step. In the operation step, the position on the measuring plate corresponding to the measuring object position is calculated based on the positional relationship between the specified scale lines and the measuring object position in the picked-up image. Thus, the position on the measuring plate corresponding to the measuring object position can be speedily and accurately detected. As a result, the measuring time required for wheel alignment measurement can be shortened, which improves the measuring efficiency and the reliability in measurement.
In a preferred embodiment of the present invention the judging unit comprises: a concentric circle extracting step of extracting a concentric circle included in the picked-up image based on the picked-up image data; a curvature calculating step of calculating the curvature of the extracted concentric circle; and a concentric specifying step of specifying the concentric circle by comparing the curvature obtained in the curvature calculating step with the curvatures stored in advance.
According to this embodiment, in the concentric circle extracting step, the concentric circle included in the picked-up image is extracted based on the picked-up image data. In the curvature calculating step, the curvature of the extracted concentric circle is calculated. In the concentric circle specifying step, the concentric circle is specified by comparing the curvature obtained in the curvature calculating step with the curvatures stored in advance. Thus, the concentric circle included in the picked-up image can be surely specified, and the position can be accurately specified. As a result, the wheel alignment can be accurately measured.
In a preferred embodiment of the present invention the wheel alignment measuring method comprises: an image pick-up step of generating picked-up image data by picking up an image of the measuring surface so that at least a part of at least one of the concentric circles and at least a part of the scale lines are included in the picked-up image; a color separation step of generating color separation picked-up image data by performing color separation on the picked-up image data; a judging step of judging which concentric circle is included in the image picked up in the image pick-up step based on the color separation picked-up image data and the curvature of the concentric circle in the picked-up image; a scale line specifying step of specifying the scale lines included in the picked-up image based on the judgment made in the judging step and the color separation picked-up image data; and an operation step of calculating the position on the measuring plate corresponding to a measuring object position, based on the relationship between the specified scale lines and the measuring object position in the image picked up in the image pick-up step.
According to this embodiment, in the image pick-up step, an image of the measuring surface is picked up so that at least a part of at least one of the concentric circles and at least a part of the scale lines are included in the picked-up image, and picked-up image data are then generated. In the color separation step, color separation is performed on the picked-up image data so as to generate color separation picked-up image data. In the judging step, which concentric circle is included in the image picked up by the image pick-up unit is judged based on the color separation picked-up image data and the curvature of the concentric circle in the picked-up image. In the scale line specifying step, the scale lines included in the picked-up image are specified based on the judgment made in the judging step and the color separation picked-up image data. In the operation step, the position on the measuring plate corresponding to the measuring object position is calculated based on the relationship between the specified scale lines and the measuring object position in the image picked up in the image pick-up step. Thus, the position on the measuring plate corresponding to the measuring object position can be speedily and accurately calculated through image processing. This improves the measuring efficiency and reliability in the wheel alignment measurement.
In a preferred embodiment of the present invention the wheel alignment measuring method further comprises a spin angle calculating step of calculating a spin angle by determining the inclination of the scale lines in the picked-up image with respect to a predetermined reference position.
According to this embodiment, in the spin angle calculating step, a spin angle is calculated by determining the inclination of the scale lines in the picked-up image with respect to the predetermined reference position. Thus, the spin angle can be speedily and accurately calculated in a simple manner.